In the wireless communication system, by executing wireless communications between a mobile station and a plurality of base stations disposed with a proper interval therebetween, data transmission and reception to/from the mobile station is performed. As an example of an arrangement of the base station that executes the communication with the mobile station, a hierarchical cell structure system has been well known. In the hierarchical cell structure system, in general, a base station for wide area is arranged for wireless communication in the entire relatively-wide area and one or a plurality of base stations for narrow area are arranged in a wide area for wireless communication in a local area of a part of the wide area.
Japanese Laid-open Patent Publication No. 09-247079, Japanese Laid-open Patent Publication No. 06-511128, and Japanese Laid-open Patent Publication No. 06-90198 are known as backgrounds.
With the hierarchical cell structure system as mentioned above, the wide-area base station and the narrow-area base station perform the wireless communication by using different frequency bands, respectively. Specifically, in the case where each of the wide-area base station and the narrow-area base station simultaneously transmits data to the mobile station, the wide-area base station and the narrow-area base station perform the wireless communication by using the different frequency bands in order to avoid an interference. However, since the wide-area base station and the narrow-area base station use the different frequency bands, it may necessary to independently secure a frequency band for the wireless communication used by the wide-area base station and a frequency band for the wireless communication used by the narrow-area base station. This is not effective from a viewpoint of effective use of the frequency band.
The above-mentioned technological problem may occur not only in the hierarchical cell structure system but also in the arrangement a plurality of base stations with a part of areas for the wireless communication overlapped. In the case where a plurality of base stations simultaneously respectively transmit data to the mobile station, a plurality of base stations individually need to use different frequency bands. Therefore, the effective use of the frequency band may be prevented similar to the hierarchical cell structure system.